Report on influenza viruses received and tested by the Melbourne WHO Collaborating Centre for Reference and Research on Influenza during 2025

Authors

  • Ms Vishma Ramji Varsani WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Dr Jessica E Miller WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Dr Tanya R Diefenbach-Elstob WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Mr James Barnes WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Ms Nikita Deshpande WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Ms Maha Khairbak WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Ms Olivia Lay WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Mr Cleve Rynehart WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Ms Sally Soppe WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Dr Clyde Dapat WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Dr Yi-Mo Deng WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Dr Saira Hussain WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Ms Heidi Peck WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Prof Ian G Barr WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia
  • Prof Patrick Reading WHO Collaborating Centre for Reference and Research on Influenza, 792 Elizabeth Street, Melbourne VIC 3001, Australia

DOI:

https://doi.org/10.33321/cdi.2026.50.054

Keywords:

influenza, vaccine, GISRS, surveillance, laboratory, annual report, WHO

Abstract

As part of its role in the World Health Organization (WHO) Global Influenza Surveillance and Response System (GISRS), the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne (the Centre) received 13,817 human influenza-positive samples during 2025. Viruses were analysed for their antigenic, genetic, and antiviral susceptibility properties. Selected viruses were propagated in qualified cells or embryonated hens’ eggs for potential use in seasonal influenza virus vaccines. Of the 13,817 samples received or processed, influenza A(H1N1)pdm09 viruses predominated, accounting for 46.1% of samples, compared to 21.2% for A(H3N2) viruses and 19.5% for influenza B viruses; one influenza C virus was received. Among viruses analysed at the Centre, the majority of A(H1N1)pdm09 (> 99%) and influenza B (98%) viruses were antigenically similar to their respective WHO recommended vaccine strains for the Southern Hemisphere in 2025. In contrast, only 43% of A(H3N2) viruses were antigenically similar to their respective WHO recommended vaccine strains. Of 3,307 samples tested for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir, 37 A(H1N1)pdm09 viruses showed highly reduced inhibition by oseltamivir and no influenza viruses tested showed highly reduced inhibition by zanamivir. Of 5,080 samples with sequencing of the polymerase acidic (PA) gene, no genetic markers associated with highly reduced susceptibility to baloxavir marboxil were identified.

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Dark and light blue shapes displaying the logo of Communicable Diseases Intelligence. The cover photo features a laboratory technician writing on a test tube, with other blue and red test tubes visable in the corner. The bottom of the cover features a lockup of the logo of the Australian Centre for Disease Control alongside the Commonwealth Coat of Arms.

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Published

25/08/26

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Ramji Varsani, Vishma, Jessica Miller, Tanya Diefenbach-Elstob, James Barnes, Nikita Deshpande, Maha Khairbak, Olivia Lay, et al. 2026. “Report on Influenza Viruses Received and Tested by the Melbourne WHO Collaborating Centre for Reference and Research on Influenza During 2025”. Communicable Diseases Intelligence 50 (August). https://doi.org/10.33321/cdi.2026.50.054.

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